This invention relates to a method and apparatus for cooling a hot glass fiber or filament as it is drawn from a molten glass preform in a furnace. A glass fiber is often employed as an optical waveguide, synonymously, an optical fiber. A glass preform is drawn to a fiber or filament and then coated with a protective material to maintain its strength, as known in the art.
Prior to coating the glass fiber it is necessary that it be quenched in order to realize production at relatively high rates as opposed to permitting it to cool by mere exposure to ambient temperature.
The art is aware of methods and apparatus for rapid cooling of hot glass fibers, such is shown in U.S. Pat. Nos. 4,594,088 issued to Paek et al, 4,208,200 issued to Claypoole et al, and Japanese Patent Application publication 63-159,239. Prior art methods of rapid cooling of hot glass fibers which are intended to be used as optical fibers, have included, typically, a liquid coolant bath through which the fiber is continuously vertically drawn with the liquid bath serving to quench the fiber and thus reduce the its temperature. Subsequent to passing from such liquid cooling devices, the fiber may be further treated by passing it through a gas, so as to thereby evaporate any liquid from the liquid bath which might remain upon the fiber.
Such prior art techniques and apparatus have not met with complete commercial success, however, because of the somewhat complex nature of the apparatus.